Patent Literature (PTL) 1, Non Patent Literatures (NPLs) 1 and 2 describe a technology referred to as OpenFlow (OpenFlow). In the OpenFlow, communication is regarded as an end-to-end flow, and path control, failure recovery, load distribution, and path optimization are performed on a per-flow basis.
An OpenFlow switch specified in Non Patent Document 2 includes a secure channel for communication with an OpenFlow controller corresponding to a control apparatus. The OpenFlow switch operates according to a flow table in which appropriate adding or rewriting is instructed by the OpenFlow controller.
In the flow table, a set of a matching rule (header fields) to be matched against a packet header, flow statistics information (counters), and actions defining processing content is defined for each flow (refer to FIG. 3).
When the OpenFlow switch receives a packet, the OpenFlow switch searches the flow table for an entry having a matching rule that matches header information of the received packet (refer to the header fields in FIG. 3).
When the entry that matches the received packet is found as a result of the search, the OpenFlow switch updates the flow statistics information (one or more counters), and executes processing content (e.g., transmission of the packet from a specified port, flooding of the packet, discarding of the packet, or the like) described in the action field of the entry.
On the other hand, when the entry that matches the received packet is not found as a result of the search, the OpenFlow switch forwards the received packet to the OpenFlow controller through the secure channel, and requests the OpenFlow controller to determine a path of the packet, based on the transmission source and the transmission destination of the received packet. The OpenFlow switch receives a flow entry for implementing forwarding of the packet according to this path, and then updates the flow table.
In this manner, the OpenFlow switch performs packet forwarding by using an entry stored in the flow table as a processing rule.
[PTL 1]
    International Publication No. WO2008/095010[NPL 1]    Nick McKeown and seven other authors, “OpenFlow: Enabling Innovation in Campus Networks,” Mar. 14, 2008 [on line], [Searched on Sep. 7, 2011], Internet <URL: http://www.openflowswitch.org/documents/openflow-wp-latest.pdf>.[NPL 2]    “OpenFlow Switch Specification, Version 1.1.0 Implemented (Wire Protocol 0x02),” Feb. 28, 2011, [online], [Searched on Sep. 7, 2011], Internet <URL: http://www.openflowswitch.org/documents/openflow-spec-v1.1.0.pdf>.